The present invention relates to a power transmission control device, a non-contact power transmission system, a power transmitting device, an electronic instrument, a waveform monitor circuit, and the like.
In recent years, non-contact power transmission (contactless power transmission) that utilizes electromagnetic induction to enable power transmission without metal-to-metal contact has attracted attention. As application examples of non-contact power transmission, charging a portable telephone, charging a household appliance (e.g., cordless telephone handset), and the like have been proposed.
JP-A-2006-60909 discloses a non-contact power transmission device using a primary coil and a secondary coil, for example. In the non-contact power transmission system disclosed in JP-A-2006-60909, a driver having a CMOS configuration (CMOS driver) is used as a driver that drives the primary coil, and a control circuit (timing control circuit) that prevents a shoot-through current is provided corresponding to each CMOS driver. The control circuit (timing control circuit) prevents a shoot-through current by preventing a situation in which the PMOS transistor and the NMOS transistor are turned ON simultaneously. It is effective to prevent a shoot-through current in the primary-side driver in order to prevent the driver from breaking down.
In the non-contact power transmission system disclosed in JP-A-2006-60909, a shoot-through current can be prevented by adjusting the drive timing of each transistor of the driver that drives the primary coil. However, JP-A-2006-60909 does not take measures against a short-circuit failure of each transistor.
For example, when a transistor that forms the CMOS driver has undergone an initial failure, it is desirable to detect the initial failure before performing a normal drive operation and take prompt and appropriate measures (e.g., collecting and repairing the instrument) without performing the normal drive operation from the viewpoint of safety. On the other hand, various circuits may be connected to the primary coil. Therefore, when detecting an initial failure, a stable and reliable novel failure detection method taking the operation of the circuit connected to the primary coil into consideration is necessary.
Another circuit (e.g., waveform detection circuit) is also connected to the primary coil. Therefore, in order to accurately detect an initial failure, the effects of another circuit connected to the primary coil must be taken into consideration.